This is based on the calculations in ASME B89.4.19: Performance Evaluation of Laser-Based Spherical Coordinate Measurement Systems. It can be used for both distance measurement using laser ranging techniques and for angle based measurements such as theodolites and photogrammetry. It could also be used to model optical distortions due to temperature gradients; commonly referred to as 'heat haze'. It will calculate distance errors (radial error) and angular errors (transverse error) given a number of segments of a ray or beam, the temperature the instrument uses to calculate refractive index, the average temperature over the segment, the perpendicular temperature gradient, the vacuum wavelength of the light, the carbon dioxide concentration, the atmospheric pressure and the humidity. The user must also specify the number of sub-divisions for each segment so that the curve of the ray can be plotted.